Satellite communications systems and methods are widely used for wireless communications of voice and/or data. Satellite communications systems and methods generally employ at least one space-based component, such as one or more satellites that are configured to wirelessly communicate with a plurality of wireless terminals.
A satellite communications system or method may utilize a single antenna beam covering an entire service area served by the system. Alternatively, in cellular satellite communications systems and methods, multiple beams are provided, each of which can serve distinct geographical areas in the overall service area, to collectively serve an overall satellite service area. Thus, a cellular architecture similar to that used in conventional terrestrial cellular radiotelephone systems and methods can be implemented in cellular satellite-based systems and methods. The satellite typically communicates with wireless terminals over a bidirectional communications pathway, with communication signals being communicated from the satellite to the wireless terminal over a downlink or forward link, and from the wireless terminal to the satellite over an uplink or return link. The downlink and uplink may be collectively referred to as service links.
The overall design and operation of cellular satellite systems and methods are well known to those having skill in the art, and need not be described further herein. Moreover, as used herein, the term “wireless terminal” includes cellular and/or satellite radiotelephones with or without a multi-line display; Personal Communications System (PCS) terminals that may combine a radiotelephone with data processing, facsimile and/or data communications capabilities; Personal Digital Assistants (PDA) that can include a radio frequency transceiver and a pager, Internet/intranet access, Web browser, organizer, calendar and/or a global positioning system (GPS) receiver; and/or conventional laptop and/or palmtop computers or other appliances, which include a radio frequency transceiver, for wireless voice and/or data communications. A radiotelephone also may be referred to herein as a “radioterminal,” a “mobile terminal,” a “user device,” or simply as a “terminal”.
Push-to-send radioterminal systems, methods and protocols are increasingly being used to provide “walkie talkie” capability in cellular communication systems. Radioterminals marketed by Nextel Communications, Inc., for example, can provide this capability. Such radioterminals are distinguishable by a separate push-to-send or push-to-talk button.
When push-to-send capabilities are provided over one or more proximate terrestrial base stations, using an appropriate air interface protocol, an acceptably low push-to-send delay may be provided. However, there is an increasing desire to provide push-to-send capability over a large geographical region and even to provide nationwide, continent-wide, and/or even global push-to-send capability. Unfortunately, in these wider geographic regions an unacceptable delay, on the order of three or four seconds or more, may be produced.